Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional. PAH is necessary to metabolize the amino acid phenylalanine (Phe) to the amino acid tyrosine. When PAH activity is reduced, phenylalanine accumulates and is converted into phenylpyruvate (also known as phenylketone). Left untreated, PKU can result in mental retardation, seizures and other serious medical problems. Currently, there is no cure for the disease and standard of care is through management of diet, minimizing foods that contain high amounts of protein.